1. Field of the Invention
The present invention relates to a data recording/reproducing apparatus utilizing a recording medium which allows digitized audio signals or the like to be arbitrarily recorded, for example, on recordable compact discs.
2. Description of the Prior Art
Heretofore, there have been widely used so-called compact discs, in which continuous data such as musical data are recorded as digital signals by means of optically detectable minute bits. The compact discs are adapted for playback by an optical disc player exclusively provided for playing them back.
FIGS. 13 and 14 are schematic views for explaining a signal format used in compact discs. As shown in FIG. 13, one frame 101a of recording signals is composed of a frame synchronizing signal 101b showing the head of the frame 101a, a subcode 101c showing additional data pertaining to primary data, and a data field 101d containing 24-byte data, which is the primary data, and a parity code for error detection/correction added to the primary data. It is noted that the data field 101d is provided by an error detection/correction system in which CIRC (Cross Interleaved Reed Solomon Code) incomplete interleave is combined.
As shown in FIG. 14, a sector 102a is made up of the 98 frames 101a, and a subcoding frame 102c is made up of the 98 subcodes 101c, showing track number (for musical primary data, called music number), absolute address data on the disc, and the like.
The time length of the sector 102a is 1/75 sec. and therefore 75 sectors correspond to 1 sec. A sector number is given by min.--sec.--frame data (where the frame is in base-75 system), forming time data and position data increasing from the innermost circumference of the disc and on stepwise.
Further, a data field 102d within the sector 102 is composed of 2352-byte primary data and 784-byte parity by a 98-frame architecture; with audio data allocated to primary data, according to a compact-disc format, a sampling frequency thereof is 44.1 kHz, a quantization is by 16 bits, and the number of channels is 2 (stereo), and therefore the amount of data per second is
(44.1 kHz.times.16.times.2)=1.4112 Mbits=176.4 k bytes, and the amount of data per sector is
(176.4 k bytes/75)=2352 bytes, which are allotted to the aforementioned primary data.
FIG. 12 is a schematic view showing an area location on a compact disc. A compact disc 100 is made up of a primary data recording area 100b, which contains primary data, such as musical data, and sector numbers by means of the subcode, and a TOC (Table Of Contents) area 100a where additional data pertaining to individual primary data recorded on the primary data recording area 100b are represented by the subcode, the additional data including, for example, track numbers, recording-start sector numbers for individual tracks, and information for discriminating whether the track is allocated to audio data, such as music, or computer-oriented data. With the above-described format, a compact disc player reads the subcode data of the TOC area 100a at the time of the disc being loaded to recognize the amount of individual primary data (for musical data, corresponding to the number of musical pieces), the sector number of its corresponding recording-start position, and the type of data (audio data or other data), thereby allowing desired tracks to be reproduced in response to a subsequent reproduction instruction promptly by access operation by making cross-reference between the data of the TOC area 100a and the sector number by the subcode of the primary data recording area 100b.
These compact discs are recorded with a constant linear velocity, or in the so-called CLV (Constant Linear Velocity) system in the recording mode, and therefore the resulting recording density is constant at any position on the compact disc, thus achieving enhanced recording capacities. In actual compact disc players, the rotation of a compact disc is controlled so that the time intervals of reproducing signals from the compact disc that has been CLV-recorded on the aforementioned signal format, for example, those of the frame synchronizing signals coincide with a reference time length, thereby accomplishing a CLV control.
From a different viewpoint, when such rewritable discs as magneto-optical discs under the recent years' aggressive development are employed with various types of data such as musical data or computer data recorded thereon, it desirable to offer such disc recording/reproducing apparatus as are common in the reproducing system to the conventional compact discs and have compatibility therewith.
In such a case, especially in an initial compact disc that has not undergone data recording, there exist no absolute address data using the subcode by the aforementioned signal format for the compact disc, or frame synchronizing signal as employed for the CLV control, or any other things. Therefore, it is impossible to perform the access operation to any arbitrary sector prior to recording, or do the CLV control needed even during recording.
Thus, there has been proposed a system of recording absolute addresses equivalent to the absolute address data by the aforementioned subcode, in which an absolute address is biphase-mark modulated and thereafter the guide recess of an optical disc is shifted radially inward or outward of the optical disc or the width of the guide recess is changed, depending on whether each bit is "1" or "0" (see Japanese Patent Laid-Open Publication No. 64-39632).
With the above arrangement, if the frequency band for the absolute address in biphase-mark modulation and that for the recording data in EFM (Eight to Fourteen Modulation) is differentiated from each other, it is possible to separate them from each other and reproduce as such and moreover to make access operation using the absolute address with the aid of the guide recess even for areas having no recording data. Besides, by using reproducing carrier components of the absolute address, an accurate CLV control can be provided, which may be effected even during recording.
However, the above-described disc recording/reproducing apparatus using rewritable discs is only capable of recording during the recording operation, as is also the case with tape recorders using compact cassettes or the like that are conventional data recording/reproducing apparatus of most common consumer use. Moreover, since the disc recording/reproducing apparatus is a single-purpose processing apparatus which works exclusively for reproduction during a reproducing operation, it can perform neither concurrent reproduction for any other purpose during a recording operation nor concurrent recording for any other purpose during a reproducing operation.
For example, when the contents of playing performance using a plurality of musical instruments are recorded and edited for each instrument, it is conceivable that one instrument is first played and recorded, and while the recorded contents are being reproduced to verify them by ear, another instrument is played to record over the former. In such a case, however, there would arise the need of a plurality of recording/reproducing apparatus and a plurality of recording media, involving increased location space and costs, as well as the need of operating simultaneously the plurality of recording/reproducing apparatus with the result of degraded operability.
Indeed, there have been available business-use recording/reproducing apparatus such as multi-track recorders, which have a number of recording channels and can perform recording and reproduction independently of each other for each channel, but they are very expensive and complex in operation due to its multifunction, thus not lending themselves to friendly consumer use.
Further, in so-called `karaoke` systems, which are recorded instrumental music systems to accompany live singing, increasing popular for household consumer use, it may often be desired to record the contents of having sung to the reproduced instrumental accompaniment in the way of mixing. In such a case, also, there would arise the need of a recording medium and reproducing apparatus for reproducing the contents of the instrumental accompaniment, as in the above case, as well as the need of another recording medium and recording apparatus for recording audio data of having done the mixing, while both of the apparatus would be necessarily operated simultaneously, which would be very laborious work to a disadvantage.
Moreover, it is undesirable that those playing-side recording medium and recording-side recording medium exist separately, because complex work will be involved in the storage and control of these recording media.